Recently, large and heavy projection devices with cathode ray tubes (CRT) have been gradually replaced by liquid crystal display (LCD) projection devices and digital light processing (DLP) projection devices. The liquid crystal display (LCD) projection devices and the digital light processing (DLP) projection devices has advantages of lightness, thinness good portability and direct connection to a digital product for displaying an image. With the development of the projection devices, the projection devices not only are widely applied for a presentation in various fields, for example, companies, schools and other public places, but also are used to see a movie at home for an ordinary family.
Generally, a focus length of the projection device is adjusted according to a distance between a projection device and a projection screen so that an image may be displayed on the projection screen clearly. Referring to FIG. 1, a projection device 100 includes a case 110, a zoom lens module 120, and focus adjusting ring 130. The case 110 defines a light emitting opening 112 and an adjusting hole 114. The zoom lens module 120 is disposed in the case 110 and corresponds to the light emitting opening 112 so that an image may emit out of the case 110 through the light emitting opening 112.
The adjusting hole 114 of the case 110 is located above the zoom lens module 120 and is configured for exposing a portion of the focus adjusting ring 130. Accordingly, a user may adjust the focus length of the projection device 100.
Referring to FIG. 2, a user may adjust the focus length of the projection device 200 by turning the focus adjusting ring 230 exposed from the light emitting opening 212.
Additionally, the image may be enlarged in the limited distance between the projection device and the projection screen on a condition that the volume of the projection device is not increased. Referring to FIG. 3, a projection device 300 is developed. The projection device 300 further includes a reflecting component 340 disposed in front of a zoom lens module 320. The reflecting component 340 is configured for reflecting the image from the zoom lens module 320. Thus, the image may emit out and pass through a top opening (not labeled) of the case 310.
As depicted in FIG. 3, if an adjusting hole (not shown) exposing a focus adjusting ring (not shown) is disposed above the zoom lens module 320, a hand of a user for turning the focus adjusting ring will locate at a light reflecting path R of the image to block the image. Thus, the image does not be displayed on the projection screen entirely. As a result, the user can not adjust the focus length of the projection device 300 according to the definition degree of the image displayed on the projection screen. Moreover, the focus adjusting ring can not be disposed in front of the zoom lens module 340 to be turned.